test_nfs.py: switch to tasks.config_replica_resolvconf_with_master_data()
    
    Previously test_nfs.py would implement its own method to configure
    resolv.conf leading to cleanup failures in some cases.
    Use tasks.config_replica_resolvconf_with_master_data() instead.
    Also simplify and fix client uninstall.
    
    Fixes: https://pagure.io/freeipa/issue/7949
    Signed-off-by: François Cami <fcami@redhat.com>
    Reviewed-By: Sergey Orlov <sorlov@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>